The effect of solvent selection in the gas chromatographic analysis of carbonyls in air samples after derivatization with pentafluorophenyl hydrazine

Abstract

Carbonyl compounds are an important component of atmospheric chemistry with the potential to form secondary pollutants (in gaseous and/or particulate forms). For their analysis, derivatization by pentafluorophenyl hydrazine has been applied in gas chromatography (GC) or high performance liquid chromatography (HPLC). Because of the need for an appropriate solvent, we have evaluated the relative derivatization performance of five solvents (methanol, pentane, hexane, dichloromethane, and water) for GC analysis. Six light and common (C-1-C-5) aldehydes (i.e., formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, i-valeraldehyde, and valeraldehyde) out of a large member of carbonyl compounds were selected in this research. Anomalously large response was observed for the formaldehyde-hydrazone prepared in methanol and water, while that of acetaldehyde-hydrazone was reduced for pentane (by similar to 89%) relative to the others. If we exclude these biased cases, their response factors were in the order of: methanol ˃ pentane ˃ hexane ˃ dichloromethane ˃ water. This ordering was seen consistently in their relative recovery: methanol ˃ pentane ˃ dichloromethane hexane ˃ water. The method detection limits (ng) of the aldehyde-hydrazone (as aldehyde mass) in each solvent were in the order: 1.0 (hexane) ˂ 1.2 (dichloromethane) ˂ 1.6 (methanol) ˂ 2.5 (pentane) ˂ 4.0 (water). As such, evidence suggests that solvent should be selected carefully to optimize the GC-based quantitation of aldehyde-pentafluorophenyl-hydrazones. (C) 2015 Elsevier B.V. All rights reserved.